Alarm systems, such as fire alarm systems, typically include a plurality of notification appliances (e.g. horn/strobe units), that are installed throughout a monitored building and that are configured to be activated upon the detection of an alarm condition, such as the presence of fire or smoke. Occupants of the building may thereby be notified of potentially hazardous conditions and may evacuate the building or take other action before being harmed. It is therefore critically important that the notification appliances of alarm systems always be in good working order.
Governmental entities may require that notification appliances, and particularly those of fire alarm systems, be tested periodically to verify that such appliances are operating properly. Such testing is typically performed by one or more designated inspectors who walk through an entire monitored building and physically visit each notification appliance installed therein. The inspectors may activate each appliance for a predefined amount of time to verify functionality, and may make note of whether each appliance performed in a satisfactory manner. Particularly, an inspector may record a “pass” result for notification appliances that successfully activated their notification features (e.g. strobes, horns, etc.) and may record a “fail” result for notification appliances that failed to activate their notification features. Evaluating the functionality of notification appliances in this manner can be extremely burdensome, as it can be time-consuming and arduous to physically visit every notification appliance in a building. This is especially true for alarm systems that include a large number of notification appliances and/or that include notification appliances that are installed in parts of a building that are not readily accessible.
In order to alleviate the burden of notification appliance testing, so-called “self-test” technologies have been developed which enable notification appliances to automatically evaluate their own functionality. For example, a notification appliance that is equipped with self-test capability may include one or more sensors, such as a microphone, sound detector, camera, photo eye, light detector, etc., located adjacent the appliance's notification features (e.g. strobes, horns, sirens, etc.). Upon executing a self-test of such a notification appliance, such as may be initiated from a centrally located alarm panel or workstation within a monitored building, the notification appliance may activate its notification features for a predefined amount of time. While the notification features of the appliance are active, the sensors may measure the output generated thereby. If it is determined from the measurement that the notification features successfully generated output, a “pass” result may be automatically recorded by the appliance. Conversely, if it is determined that the notification features failed to generate output, a “fail” result may be automatically recorded by the appliance. The self-test feature thereby relieves inspectors from having to physically visit, manually test, and observe each appliance in an alarm system to effectuate a functional test.
One shortcoming associated with existing self-test technologies is that the sensors of a notification appliance that is being self-tested do not discriminate between output generated by the notification features of the notification appliance and ambient sound or light produced by other sources. Therefore, when the output of such notification features is measured during self-testing, a particularly strong source of ambient sound or light produced by a source other than the notification features could result in a so-called “false positive.” That is, a notification appliance having a defective notification feature that would normally fail a self-test may measure ambient sound or light generated by a nearby device, and may mistakenly interpret such sound or light as output generated by its own notification features, thereby causing the notification appliance to erroneously record a “pass” result for the self-test. One example of such a situation would be a loud lunch bell ringing in the vicinity of a fire alarm horn that is being self-tested.